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    <title>Document</title>
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    <script>
      const obj = { num: 1 }
      const obj2 = obj
      obj2.num = 2
      console.log(obj.num)

      let a = 10
      let b = a
      b = 20
      //   a===10
      //   const obj = { num: 1 }
      //   const arr = []
      //   arr.push(obj)
      //   arr[0].num=2
      //   obj.num=?
    </script>
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